CHICAGO, Illinois - Five people have been shot dead and a number of others wounded by a gunman at an industrial park in the outer metropolitan area of Chicago.

The gunman was also killed, in a shoot-out with police, which resulted in 5 officers suffering gunshot wounds.

Five people were killed and several others injured when a gunman opened fire at an industrial park in the US state of Illinois, police there say.

The gunman who police have identified as Gary Martin, aged 45, was reportedly made redundant recently at the Henry Pratt Company manufacturing plant at Aurora, a Chicago suburb, where the shootings took place.

Police received muliple calls of an active shooter in Aurora at about 1:24pm local time Friday, Aurora Police Chief Kristen Ziman said at a press conference at the Aurora Police Department shortly after 9:00pm Friday night.

"At 1:28pm officers arrived and they were fired upon immediately. Two of the four officers that entered the building were shot," she said.

Additional officers arrived and entered the building, a warehouse, which police said comprised 29,000 square feet. When they located the gunman they exchanged fire with him and he was shot and killed, Ziman said.

"These officers and their colleagues did not hesitate to literally put their lives on the line today to stop further bloodshed," Chris Southwood of the Illinois Fraternal Order of Police said in a statement released on Friday.

Two of the 5 police officers wounded were airlifted to Chicago area trauma centres.

"I don't think I can be clearer that saying today is a sad day today," Aurora Mayor Richard Irvin said at the press conference,

"In so many years we have seen similar situations throughout our nation."

"It's a shame that mass shootings like this have become commonplace in our country," he said.